As disclosed for example in Patent Documents 1 and 2, ordinary drive apparatuses provided in a hybrid vehicle include engines such as gasoline engines or diesel engines, and electric motors such as motors or motor/generators. Engines and electric motors are combined in various forms, and the number of electric motors used is not limited to one; multiple electric motors are sometimes used.
Patent Documents 1 and 2 disclose hybrid vehicles in which two electric motors are used. In these hybrid vehicles, an engine, a first motor/generator and a second motor/generator are linked to each other via a power division mechanism constituted from a planetary gear mechanism. Power of a ring gear of the planetary gear mechanism is transmitted to drive wheels via a power transmission mechanism. Thus, power of one or both of the engine and the second motor/generator can be output to the drive wheels.
In this type of hybrid vehicle, by controlling driving and stoppage of the engine and the motor/generators based on various conditions, running is possible by engine running, which is a running mode of running by driving only the engine, EV running, which is a running mode of running by driving only the motor/generators while not driving the engine, or engine/motor running, which is a running mode of running by driving both the engine and the motor/generators. Switching between these running modes can be performed automatically, or by manual operation of a driver.
When switching from EV running to engine/motor running, starting of the stopped engine is performed by an engine start control apparatus. At that time, the engine start control apparatus executes cranking by powering the first motor/generator, which is coupled to the engine. When the engine reaches a predetermined revolutions, fuel injection and ignition are performed to start operation of the engine.
In the hybrid vehicle, starting/stopping of the engine is repeatedly executed during running. Accordingly, in order to insure a comfortable ride, smooth starting of the engine is sought. In order to realize smooth engine starting, fuel injection and ignition are performed after the engine revolutions have been increased by cranking to near the revolutions of self-sustaining operation. At this time, engine torque fluctuation, specifically torque fluctuation due to initial firing of the engine, is transmitted as torsional vibration via the crankshaft to various power transmission mechanisms such as the power division mechanism constituted from the planetary gear mechanism. In order to absorb this vibration, a damper that absorbs vibration is provided between the crankshaft and an input shaft. Further, in order to absorb vibration transmitted to the power division mechanism that cannot be absorbed by the damper, torque control of an electric motor (in the hybrid vehicle disclosed in Patent Documents 1 and 2 for example, the second motor/generator corresponds to this electric motor) made capable of power transmission in a power transmission path from the engine to the drive wheels is performed so that vibration that has reached the power division mechanism is absorbed. That is, a hybrid control controller that controls driving of the engine and the electric motors via an engine control apparatus and an electric motor control apparatus performs control in which an optimal corrected torque value is calculated from revolution position information, engine revolutions information, preprogrammed torsional rigidity of each component, inertia moment, hysteresis values, and so forth of the above electric motors, and the torque of the electric motors is corrected to increase or decrease. Thus, even comparatively large vibration due to engine initial firing or the like that has reached the power division mechanism is reduced. As a result, vibration that is transmitted to a differential, a drive shaft, a body, or the like on the downstream side from the power division mechanism also is reduced, and so ride comfort of the driver is improved.
Incidentally, in a hybrid vehicle, often an oil lubrication mechanism is provided in which an oil pump is operated by rotation of an engine output shaft, and supplies lubricating oil from this oil pump to the power division mechanism or the like. During EV running, the engine and the oil pump are both stopped, so this type of oil lubrication mechanism stops supplying lubricating oil to the power division mechanism during EV running. When such a state continues for a long time, there is a risk that heat damage will occur due to inadequate lubrication within the power division mechanism.
Therefore, in the hybrid vehicle disclosed in Patent Document 2, during EV running, rotational torque of the first motor/generator is transmitted to a rotating shaft for operating the oil pump at a predetermined timing, and thus the oil pump is operated for a fixed period of time to supply lubricating oil to the power division mechanism and the like. With this configuration, even during EV running of the hybrid vehicle, lubricating oil is supplied to the power division mechanism for the necessary time period at an appropriate timing, thus preventing heat damage to components to which supply of lubricating oil is stopped while operation of the oil pump is stopped.